[PATCH 1/9] serial: core: move RS485 configuration tasks from drivers into core

[Lino Sanfilippo]

Several drivers that support setting the RS485 configuration via userspace
implement on or more of the following tasks:

- in case of an invalid RTS configuration (both RTS after send and RTS on
  send set or both unset) fall back to enable RTS on send and disable RTS
  after send

- nullify the padding field of the returned serial_rs485 struct

- copy the configuration into the uart port struct

- limit RTS delays to 100 ms

Move these tasks into the serial core to make them generic and to provide
a consistent beheviour among all drivers.

Signed-off-by: Lino Sanfilippo <LinoSanfilippo at gmx.de>
---
 drivers/tty/serial/serial_core.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 846192a7b4bf..3fab4070359c 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1282,8 +1282,21 @@ static int uart_set_rs485_config(struct uart_port *port,
 	if (copy_from_user(&rs485, rs485_user, sizeof(*rs485_user)))
 		return -EFAULT;
 
+	/* pick sane settings if the user hasn't */
+	if (!(rs485.flags & SER_RS485_RTS_ON_SEND) ==
+	    !(rs485.flags & SER_RS485_RTS_AFTER_SEND)) {
+		rs485.flags |= SER_RS485_RTS_ON_SEND;
+		rs485.flags &= ~SER_RS485_RTS_AFTER_SEND;
+	}
+	/* clamp the delays to [0, 100ms] */
+	rs485.delay_rts_before_send = min(rs485.delay_rts_before_send, 100U);
+	rs485.delay_rts_after_send = min(rs485.delay_rts_after_send, 100U);
+	memset(rs485.padding, 0, sizeof(rs485.padding));
+
 	spin_lock_irqsave(&port->lock, flags);
 	ret = port->rs485_config(port, &rs485);
+	if (!ret)
+		port->rs485 = rs485;
 	spin_unlock_irqrestore(&port->lock, flags);
 	if (ret)
 		return ret;

base-commit: ad30d108a5135af584ff47f5ff81be971b6c26f1
-- 
2.34.1